The use of spinal rods is conventional for correction of spinal trauma or conditions, such as curvature of the spine. Generally, an orthopedic stabilization system may include a pair of elongate members, such as spinal rods or plates, that are coupled to a bone or bones. For the sake of simplicity, the term “rod” is used throughout to refer to any elongate member. The rods are generally contoured and longitudinally disposed adjacent to vertebral bodies of a spine.
The strength and stability of the rod assembly can be increased by coupling the two rods with a cross-connector that extends substantially horizontal to the longitudinal axes of the rods across the spine. In some situations, the two rods are geometrically aligned such that the two rods are parallel to each other. However, the two rods are often not three dimensionally geometrically aligned in actual situations. There are several ways to address the variations of geometrical alignment. First, one or both of the rods can be bent to accommodate the transconnector. However, any bending in either of the rods can adversely affect the fixation to the spine and comprise clinical outcome. Furthermore, the bending can also adversely affect the mechanical properties of the rods. The transconnector can also be bent so that the disturbance to the rod positioning is minimized. As is the case with bending of the rods, the mechanical properties of the transconnector could be compromised.
Because of the forces acting along the transverse connector and the movement of the spinal rods, the connection between the transverse connector and the rod must be secure to avoid movement of the transverse connector along the spinal rod. Some rod fastening systems of transverse connectors use threaded fasteners to attach the transverse connector to adjacent rods. The threaded fastener can be a setscrew or a nut. Not tightening a threaded fastener enough may allow movement of the transverse connector. Overtightening a threaded fastener could result in damage to the system and failure of the transverse connector.